Exercise

The benefits of regular exercise for general health are well known, and in recent years the association between regular exercise and improved cognitive function has been reviewed in the literature.1-3

Exercise may be beneficial for individuals with ADHD,4,5 although the majority of supporting studies are limited in size.

A meta-analysis of eight randomised controlled trials assessing the effects of physical exercise in children with ADHD (n=249) indicated that short-term aerobic exercise was effective in alleviating impairments in attention, hyperactivity, impulsivity, anxiety, executive function and social disorders.6 However, the authors concluded that the results should be viewed with caution given the small number of studies and the heterogeneity of the outcomes.6

Other studies that investigated the effects of exercise on symptoms of ADHD include:

A study of a 10-week moderate-to-high–intensity exercise programme in children with ADHD (n=21, aged 7–12 years). Significant improvements versus controls were seen on three subscales of the Child Behavioural Checklist (thought problems, attention problems and social problems).7

An investigation of the effects of a 30-minute moderate-intensity aerobic exercise session in children with ADHD (n=40). A control group of children watched a running/exercise-related video. Following the exercise session, children with ADHD demonstrated improvements in Stroop Test and Wisconsin Card Sorting Test performance (non-perseverative errors and categories completed). No improvements were seen in the control group.8

Pontifex et al investigated the effect of a 20-minute moderate-intensity aerobic exercise session in pre-adolescent children with ADHD (n=20; aged 8–10 years). Task performance and event-related brain potentials were measured whilst participants performed an attentional-control task. Following the exercise session, greater response accuracy and stimulus-related processing were observed in both children with ADHD and matched controls. Children with ADHD also showed selective enhancements in regulatory processes following exercise, compared with after a reading exercise.4

In a pilot study of adults with ADHD (n=30; mean age 27.3 years), those who engaged in frequent aerobic physical activity had reduced behavioural impulsivity and less worrisome thoughts compared with those who engaged in non-frequent physical activity.5

Diet

Many small studies have assessed the effects of dietary interventions for the management of ADHD symptoms – such as restriction or elimination diets, or dietary supplementation with iron, vitamins, minerals and omega-3/6 fatty acids.9-13

Fatty acid supplementation

In a large observational study in children with ADHD aged 5–12 years (n=810), omega-3 and omega-6 fatty acids in combination with supplementary magnesium and zinc showed a beneficial effect on attentional, behavioural and emotional problems.14

A meta-analysis of eleven probably-blinded studies by Sonuga-Barke et al11 reported small but significant (p=0.04) reductions in ADHD symptoms in association with free fatty acid supplementation (Figure). Five of the eleven studies assessed the effects of omega-3 supplements, two studies assessed omega-6 supplements, and four studies assessed both omega-3 and omega-6 supplementation. Free fatty acid supplementation effects remained significant when only the nine trials with no/low medication use were considered (standardised mean difference 0.17; 95% confidence interval [CI] 0.01–0.34).11

Artificial food colourings

In the same meta-analysis, dietary exclusion of artificial food colours had a statistically significant effect on symptoms of ADHD (p=0.004), although the participants in these studies were often predisposed to food sensitivities (Figure).11

Artificial food colour exclusions. Reproduced with kind permission.11

Further cautious support for the potential benefits of eliminating artificial food colourings from the diet of patients with ADHD comes from a meta-analysis published in 2012.33 This study estimated that a restrictive diet may improve ADHD symptoms in around 30% of children with ADHD (data from six placebo-controlled studies; n=195).

The study authors concluded that although the effects of artificial food colourings on symptoms of ADHD were notable and warranted further investigation, they were susceptible to publication bias or were derived from small, non-generalisable samples.33

Micronutrients

In a randomised controlled trial investigating the efficacy of micronutrient treatment (which contained all vitamins with the exception of Vitamin K, and 16 minerals) in adults (aged ≥16 years) with ADHD over 8 weeks, 42 patients received the supplement and 38 patients received placebo.10

Significant inter-group differences on the self- and observer-rated Conners’ Adult ADHD Rating Scale (CAARS) for total Diagnostic and Statistical Manual of Mental Disorders (DSM) ADHD symptoms favoured treatment with micronutrient supplementation (p=0.009 and p=0.026, respectively); this was not observed for the clinician-rated CAARS DSM ADHD ratings10

There were no inter-group differences in Montgomery–Åsberg Depression Rating Scale score.10

There is a lack of specific clinical guidance governing the use of physical exercise or dietary interventions in ADHD – current recommendations, including National Institute of Health and Care Excellence (NICE) guidelines, advocate the importance of regular exercise, a balanced diet and good nutrition for children, adolescents and adults with the disorder.34

Stevenson J, Buitelaar J, Cortese S, et al. Research review: the role of diet in the treatment of attention-deficit/hyperactivity disorder–an appraisal of the evidence on efficacy and recommendations on the design of future studies. J Child Psychol Psychiatry 2014; 55: 416-427.